JP2003248970A - Optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium that has small warping and excellent electric characteristics even if there are changes in environments. <P>SOLUTION: An optical recording medium has, at least, a reflector film, a light transmissive layer formed in this order on a base plate made of thermoplastic resin, and information recording and reproduction are made from the side of the light transmissive layer. The optical recording medium is characterized in that a support base plate is composed of polymer containing a cycloaliphatic structure as the main chain structure, and that the grooves and/or bits formed on the support base plate or the light transmissive layer have bottom surfaces whose center line average height (Ra) is within a range of 0.10 nm to 0.70 nm. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high density optical recording medium which can cope with a high numerical aperture and a short wavelength of an optical head.

[0002]

2. Description of the Related Art Conventionally, as a substrate material for optical recording such as an optical disk and an optical card, a polycarbonate resin and a polymethylmethacrylate resin have been widely used because they are excellent as optical materials. Among them, polycarbonate resin is widely used as a substrate material for optical discs because it is excellent in transparency, heat resistance stability and toughness.

In recent years, the capacity of optical (magneto-optical) recording disks has been increased, or the recording density represented by the development of DVDs and the development of blue lasers has been increasing. The thickness of the disc substrate is as thin as 1.2 mm for a CD and 0.6 mm for a DVD, and as a next-generation optical disc, a light transmission layer having a thickness of around 0.1 mm and a support substrate of about 1.1 mm are used. The structure consisting of pasting is becoming mainstream.

As a required characteristic of the supporting substrate, a material having excellent rigidity is required from the viewpoint of reducing the warp of the medium, and several proposals have been made. For example, JP-A-9-147417 and JP-A-11-185.
Japanese Patent No. 291 describes polycarbonate, metal, and glass. Further, JP-A-10-154351 discloses metals such as Al and Ni, glass, and reinforced plastic. However, metal and glass are not only poor in productivity but also heavy. Further, in the case of glass, there is a drawback that it is easily broken. In the case of polycarbonate and reinforced plastic, although these points are relatively good, it has been found that there is a problem of warp fluctuation due to environmental changes. In other words, in the next-generation medium, the distance between the medium and the head is small, so that not only the warp of the medium is small, but also the change of the warp is required to be small due to environmental changes such as temperature and humidity. ing. However, polycarbonates have been found to be inadequate in this respect.

In order to obtain better electric characteristics, it is necessary that the surface roughness of the grooves and pits is small. For example, even if the same stamper is used, the surface roughness of the grooves and pits can be reduced by using a polycarbonate resin. Becomes larger,
Also in this respect, the polycarbonate resin is insufficient.

Regarding the surface roughness, there have been some proposals in the past. For example, Japanese Unexamined Patent Publication No. 11-134711 describes that "there is no height higher than ¼ of the laser wavelength". However, this has a problem of collision with the floating optical head, and therefore, for example, when the laser wavelength is 4
If it is 00 nm, it has a very large numerical value of 100 nm. Further, in JP-A-2001-273675, it is described that the average surface roughness is 10 nm or less, and in Examples, those having a surface roughness of 3 to 8 nm are described. Further WO
In Japanese Patent Laid-Open No. 2000/48172, R is included in the claims.
It is described that a is 10 nm or less.

As described above, the smallest specific description regarding the centerline average roughness is 3 nm, but as a result of studying this point, the present inventors have found that the centerline average roughness (Ra) is 1 nm. Even if there is, I found that there is a problem in the electrical characteristics.

As described above, the conventionally proposed support substrate can satisfy the required characteristics such as good productivity, low material cost, good dimensional stability against temperature and humidity, and excellent electrical characteristics. There wasn't.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical recording medium which has such a problem, in particular, a small change in warp even when the environment changes, and which has excellent electric characteristics.

[0010]

The present inventors have arrived at the present invention as a result of extensive studies on this problem. That is, the present invention provides an optical recording medium in which at least a reflective film and a light transmitting layer are sequentially formed on a supporting substrate made of a thermoplastic resin, and information is recorded and / or reproduced from the light transmitting layer side. The substrate is composed of a polymer having an alicyclic structure in the main chain, and the center line average roughness (Ra) of the bottom surface of the grooves and / or pits formed on the surface of the supporting substrate and / or the light transmitting layer is 0. 10 nm to 0.70 nm
The optical recording medium is characterized in that

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A polymer having an alicyclic structure in the main chain used for a supporting substrate, which is one of the features of the present invention, will be described. The term “main chain” as used in the present invention refers to a range that can be traced along the bond in the length direction of the polymer with a single stroke without passing through the same bond. For example, in the figure (A) below, a → b
→ c → d → e → f → g → h → c → b → i If you trace the bond with b → c, you have to pass twice between b and c, so the main chain is a–b
−i. The cyclohexane structure is the side chain. On the other hand, in (B), a → b → c → d → e → h, or a → b → c → f → g → e → h becomes a route other than a → b → h, and they do not pass the same bond. . Therefore, this norbornane structure also becomes the main chain. In (C), (D), and (E), the norbornane structure is also referred to as the main chain for the same reason.

[0012]

[Chemical 5]

[0013]

[Chemical 6]

[0014]

[Chemical 7]

[0015]

[Chemical 8]

[0016]

[Chemical 9] In addition to the alicyclic structure, the main chain of the present invention has the above (B)
(C) as shown in the ethylene structure (-CH ₂ -CH
_There may be an alkene structure such as _2- ) or an aryl structure. The main chain of these and the alicyclic structure is composed of carbon-carbon bonds. This carbon-carbon bond may be a double bond, but the double bond in the aliphatic hydrocarbon is thermochemically unstable, so it is preferable not to have it. In the case of a phenyl group or an aryl group, since it is stabilized by delocalization of π electrons, there is no problem even if it exists.

However, in order to minimize the influence of water absorption, which will be described later, it is more preferable to hydrogenate and form only a single bond. Further, the element bonded to the carbon atom may be bonded to not only carbon and hydrogen but also other elements.

Examples of the alicyclic structure include cycloalkane and cycloalkene, and cycloalkane is preferable in terms of heat resistance, chemical stability, water absorption and the like. From the viewpoint of heat resistance, fluidity (moldability), mechanical strength, etc., the number of carbon atoms constituting this is preferably 5 to 20. As specific examples, (1), (2), (3), (4)
However, the present invention is not limited to these.

Hydrogen atoms in these alicyclic structures may be replaced with an alkane group such as a methyl group or an ethyl group or a carboxylic acid ester group. For example, R1 and R2 in (3)
However, these are preferable from the viewpoint of synthesis and characteristics. As R1 and R2, any one of a hydrogen atom, an aliphatic hydrocarbon group having 1 to 6 carbon atoms, and a carboxylic acid ester group represented by COOR ₃ is preferably used. Here, R ₃ is preferably an aliphatic hydrocarbon group having 1 to ₃ carbon atoms.
In particular, each R1, R2, what is CH _3, COOCH ₃ is often used. Although many other configurations are possible for the alicyclic structure, the above (B), (C), (D), and (E) are low in raw material cost, easy to manufacture, and consequently obtain an inexpensive supporting substrate. It is possible because it is possible. Further, the hydrogen atom bonded to one carbon atom may be replaced with another group. Further, copolymers or blends of the substances shown in (1), (2), (3) and (4) may be used.

Substituents (side chains) bonded to these main chains,
Even in the atom, if it does not have a polar group, the polar group is not included in all the structures. As a result, the water content of the polymer is reduced, and the characteristics of the obtained optical recording medium are improved as will be described later, which is more preferable.

The molecular weight of the alicyclic structure-containing polymer is appropriately selected in consideration of its thermal characteristics, mechanical characteristics, fluidity and the like. Usually a weight average molecular weight of 5,000 to 1,000
000 g / mol, preferably 30,000 to 50,000
A range of 0 g / mol is used. If the molecular weight is too small, it is too brittle and the mechanical strength decreases. On the other hand, if it is too high, the fluidity is lowered, and there is a possibility that the transferability at the time of molding may be problematic. Therefore, it is appropriately selected in consideration of the purpose and application.
Further, (1) and (2) are (1A), (1B),
It is characterized by comprising a polymer containing (2A) and (2B). In order to maintain the characteristics of these components, it is preferable that they are contained in a total amount of 80% by weight. Each of these components may be randomly entered or may be a block copolymer in which they are continuously bonded. The ratio of these two components is in the range of 1:99 to 99: 1 and is used depending on the required characteristics.

As a synthetic method for obtaining this, a known method is used. Generally, a method of hydrogenating after ring-opening polymerization is preferably used.

If necessary, the polymer having an alicyclic structure in the present invention includes a release agent, a heat stabilizer, an ultraviolet absorber,
You may include additives, such as an antistatic agent.

The optical recording medium of the present invention has a light-transmitting layer and a supporting substrate made of the above polymer having an alicyclic structure. The thickness of the light transmitting layer tends to become thinner as the recording density improves, and is preferably in the range of 0.01 mm to 0.2 mm.
The thinner the film, the more advantageous it is for high density, but it becomes difficult to prepare a film satisfying required characteristics such as ensuring uniform thickness distribution.
From that viewpoint, 0.05 mm to 0.1 mm is preferably used.

On the other hand, the thicker the supporting substrate is, the more preferable it is in terms of mechanical characteristics. However, in practice, the thickness is selected so as to satisfy the standard of the thickness of the optical recording medium. In addition to the light transmitting layer and the supporting substrate, the optical recording medium includes an adhesive layer for bonding these, a recording layer adapted to the recording method, a dielectric layer and / or a metal reflective layer. Since the thickness of the supporting substrate is selected so that the total thickness satisfies the standard, it cannot be uniquely determined. An optical recording medium having a thickness of 1.2 mm which is generally used at present has a thickness of 1.0 mm to 1.15 mm.

The support substrate has grooves and / or pits corresponding to the recording format. Generally, the area where the groove is present is an area used by the user for writing, and the pit is where the manufacturer writes information. For example, only a pit exists in a medium called a ROM in which music and video information are recorded. In a rewritable disc called RAM,
There are both grooves and pits.

These are both obtained by transferring what is written on the stamper in the molding process. Basically, the surface shape of the stamper is designed so that the electric characteristics and the like are optimized, and in molding, molding conditions are selected so as to completely transfer it. The surface shape referred to here is land height (groove depth), land width, groove width, slope angle between lands / grooves, pit height, pit width, pit interval, and the like. However, in reality, a perfect stamper shape is not transferred due to heat shrinkage of the substrate, surface tension, molding conditions, and the like. Usually, the optimum groove considering these
A stamper with a pit shape is designed.

In addition to these apparent shapes, the surface roughness of each part of the substrate also reflects minute irregularities on the stamper surface.
Since this surface roughness causes an increase in noise of the medium,
Smaller is preferable. In particular, in an optical recording medium having a thin light transmitting layer, in order to improve the recording density, the groove width,
The land width has become smaller and this effect has become noticeable.
The unevenness of the stamper surface is influenced by the surface properties of the glass used during stamper production, the type of photopolymer, etching conditions, etc., and great efforts are being made to reduce this during stamper production.

When molding is carried out using the polymer having an alicyclic structure of the present invention, each part is formed even though the shape of the groove or pit is the same as that of a molded substrate made of another resin using the same stamper. It has been found that the surface roughness of is small. For example, the surface roughness Ra of the convex portion of the stamper (corresponding to the bottom of the groove portion in the molded substrate) is 0.62n.
When a stamper of m is used, Ra of the groove bottom of the obtained molded substrate is 0.60 nm in the case of the polycarbonate resin, whereas the surface roughness of the resin used in the present invention is as small as 0.48 nm. Become. That is,
Even if the stamper is the same, it is possible to obtain a board with less noise. In addition, Ra here means center line average roughness.

The optical recording medium of the present invention is characterized in that the center line average roughness (Ra) of the bottom surface of the grooves and / or pits formed on the surface of the substrate is in the range of 0.10 nm to 0.70 nm. And The land surface and the top surface of the pit change in the final transfer situation during molding. However, the groove and the bottom of the pit are transferred in the initial stage, and even if the transfer conditions are slightly unsatisfactory, they are determined by the stamper surface and the physical properties of the resin, and are hardly affected by the molding conditions. It is necessary that Ra there satisfies this condition. If it is larger than this, the noise of the optical recording medium becomes large. On the other hand, if it is small, not only the cost of producing such a stamper becomes high, but also the adhesiveness with a layer such as a metal film, an oxide or a nitride provided on the substrate is deteriorated. Further, it becomes difficult to manufacture such a smooth stamper, which leads to an increase in manufacturing cost.

Although this value itself changes depending on the stamper (surface state), it is necessary to set Ra of the supporting substrate within this range in order to reduce the noise of the optical recording medium regardless of the stamper state. The upper limit of this value is preferably 0.50 nm or less, more preferably 0.45 nm or less. In order to obtain a support substrate having such a surface roughness using the polymer of the present invention, a stamper having Ra of about 0.6 nm or less is used, and the temperature of the mold is in the range of about 10 ° C. to a high temperature from the heat distortion temperature. It is obtained by molding.

The Ra is measured by scanning a needle along a groove or a pit using an atomic force microscope SFA-300 manufactured by Seiko Denshi Kogyo Co., Ltd., and Ra is also evaluated at the center of the groove bottom and the pit bottom. Is the value obtained by scanning.

Next, the light transmitting layer will be described. There are two cases on one side, with and without pits and grooves. In any case, since writing and reading are carried out by laser through this layer, it is preferable that the transmittance at the wavelength of the laser light used is high.
The light transmittance at 400 nm is preferably 80% or more, more preferably 85% or more, still more preferably 90% or more. In addition, it is preferable that the heat resistance is high from the viewpoints of size and shape stability at the time of manufacturing and products. The glass transition point is preferably 100 ° C. or higher. The birefringence is preferably small in order to obtain better electric signal characteristics. Retardation is 20 nm or less, further 10 n
m or less is preferable. Further, in order to reduce the warp change due to the environmental change, it is preferable that the water absorption rate is small. AST
The evaluation by MD542 is preferably 1% or less, more preferably 0.1% or less. Further, since the thickness variation of this layer has a great influence on the electric signal characteristics, it is preferable that it is small, 5 μm or less, further preferably 1 μm or less.

Any material may be used as long as it satisfies the above conditions, but an organic polymer resin is preferably used in terms of productivity, lightness and the like. Among them, polycarbonate resin and amorphous polyolefin resin are preferable. In particular, when a polymer containing an alicyclic structure, which is the same material as the supporting substrate of the present invention, is used, the materials to be laminated are the same, mechanical balance, adhesion, etc. are not only advantageous, but the water absorption is small, and the retardation Is more preferable and the surface hardness is high.

Next, a method for manufacturing the optical recording medium of the present invention will be described.

First, the light transmitting layer will be described. As described above, this layer may or may not have grooves and pits. First, the case where it does not exist will be described.

In this case, an ordinary sheet forming method is used. The resin that has become molten by raising the resin temperature is
Melt film forming methods such as T-die method extruded from mold die, inflation method using air and injection molding method Solution casting film forming method (casting) in which a solution dissolved in an organic solvent or water is cast on a support. The method can be manufactured by a calendar method in which rolling is performed between rolls. The light transmitting layer used in the present invention may be formed by any of these methods. However, while the melt film forming method is excellent in productivity, it may cause a problem of minute thickness unevenness due to a T-die called a die line, and a problem of appearance quality due to foreign matter or gel. In addition, the calendering method also tends to cause uneven thickness.
In the case of an optical recording substrate, it is said that the thickness unevenness has a great influence on the electrical characteristics and it is necessary that the thickness be several μm or less, which is difficult with these methods. The injection molding method has a merit that the shape itself (outer shape, inner diameter hole) of the optical recording medium is completed at the same time as obtaining a sheet, but in the case of a thin thickness as in the present invention, high-speed injection, high mold temperature, The selection range of molding machine and mold molding conditions such as resin temperature is narrow.

Although the solution casting film forming method is inferior in productivity, it is possible to easily obtain a film having less thickness unevenness and surface roughness and less foreign matter and gel. The drawback of this method is that it is difficult to obtain a thick sheet, but future optical recording substrates will be thinned to around 0.3 mm, and even around 0.1 mm. In this respect as well, the organic polymer of the present invention is used. It is more desirable as a sheet manufacturing method. In addition, since the solvent is included in the sheet manufacturing process, relaxation is likely to occur and orientation is less likely to occur, and thus there is an advantage that birefringence is reduced, which is more preferable.

On the other hand, when there are grooves or pits, a method such as injection molding is used, in which a sheet is prepared by the above-mentioned sheet preparation method, then brought into contact with a stamper and heated and pressed to transfer the sheet. The injection molding method has various restrictions as described above, and it is preferable to use a solution casting film forming method and heat press the stamper.

The supporting substrate is formed by a commonly used injection molding method,
It is produced by a known method such as an injection compression molding method.

The optical recording medium of the present invention is a medium such as an optical card or an optical disk for performing recording and reproducing by using light. Particularly, it is preferably used for a circular optical disk.
For example, as a rewritable disc, a magneto-optical recording medium, a recording medium using phase change, a once-writable medium using a dye or the like (referred to as -R), and signals are recorded from the beginning in the form of pits. It is used as a recording medium (called -ROM). Various recording layers, reflective layers, protective layers, protective resin layers, etc. are formed on these in accordance with the purpose. As a method of bonding the support substrate provided with these and the light transmission layer, a known method such as an ultraviolet curable resin, a hot melt resin, an adhesive sheet is used.

[0042]

The optical recording medium of the present invention has a thin light transmitting layer and a supporting substrate, has a small warp change with respect to environmental changes,
It is also an optical recording medium with little noise. It is an optical recording medium for high-density information recording, which is advantageous for recording required for high-density recording in the future, a shorter reading wavelength, and a higher numerical aperture of an optical head.

The present invention will be described in detail below with reference to examples. However, the present invention is not limited to these examples.

Materials and measuring methods used in this example and comparative examples will be described. 1) Dimensional stability evaluation Media warpage was measured in a clean room environment (25 ° C, 50% RH), and then measured with a temperature / humidity tester (30 ° C, 90% RH).
After holding for a day, the medium is returned to the clean room environment again, and the change in warp with time is tracked. 2) Warpage measurement High precision laser angle measuring device LA-200 manufactured by Keyence Corporation
0, the radial direction Tilt (R-Tilt) of the medium was measured. Since the laser light is incident from the light transmitting layer side, the symbol − means concave on the light transmitting layer surface, and + means concave on the supporting substrate side. 3) Surface Roughness Measurement Method The measurement by AFM was performed by the following method.

Measuring device: SEIKO Electronic Industry (currently SEIKO Instruments) Co., Ltd. SFA-300 Measurement cantilever: SEIKO Instruments Co., Ltd. SI-AF01 Measurement conditions: Scanning width 5 μm Scanning speed 10 μm / sec Scanning direction Shape measurement --- Disk radial direction (perpendicular to the groove) When measuring surface roughness --- Disk circumferential direction (parallel to the groove) Ra was evaluated by measuring the center of the groove part (pit part) of the above surface roughness measurement image with the groove. Scan in the direction (circumferential direction)
I asked for a. This was repeated 8 times in another groove (pit) and the average value was obtained. 4) Disk noise measuring method <Medium production> ZnS-SiO2 (95 nm), GeSbT was formed on the substrate.
e (20 nm), ZnS-SiO2 (15 nm), Al
-Cr (150 nm) was sequentially deposited. <Evaluator> Pulstec Industrial Co., Ltd. DDU-1000
(650 nm pickup) was used. <Evaluation conditions> Measurement position: radius 25r, groove, reproduction laser power: 1 mw, linear velocity: 6 m / sec, measurement band: 0 to 1
0 MHz

[0046]

[Example 1] Zeonex 280R manufactured by Nippon Zeon Co., Ltd.
Was used to prepare a light transmission layer and a supporting substrate.

First, for the light transmitting layer, the polymer was dissolved in toluene to obtain a polymer solution having a concentration of 33% by weight. This polymer solution was filtered with a 1.0 μm membrane filter and cast on a glass plate using a doctor blade with a clearance of 300 μm. After this was left at 25 ° C. for 10 minutes, it was dried by gradually raising the temperature from 60 ° C. to 150 ° C. in a hot air dryer. After drying, the film was peeled from the glass substrate to obtain a transparent sheet having an average film thickness of 100 μm. The transmittance of this sheet at 400 nm was 89.8%. Further, as a result of measuring birefringence, the retardation was 6.5 nm when the incident angle was vertical, and 8.8 nm when the incident angle was 30 degrees.
Met. Further, when the thickness of a 20 cm square sheet was measured longitudinally and transversely with a micrometer at 1 cm intervals, 100 ± 1 μm was satisfied at all measurement points. The water absorption was 0.01% or less, and the pencil hardness was H to 2H.
This was cut into a size having an outer diameter of 120 mm and an inner diameter of 15 mm to obtain a light transmitting layer.

The supporting substrate is a disk molding machine MO40D3H manufactured by NISSEI RESIN CO., LTD.
A substrate having a thickness of 20 mm and a thickness of 1.1 mm was obtained. Resin temperature is 3
The temperature was 30 ° C. and the mold temperature was 125 ° C. A stamper having a track pitch of 0.6 μm and a groove depth and a pit depth of 40 nm was used. The substrate obtained by molding is
It was confirmed by AFM measurement that it had the same shape. Ra of the groove bottom of this substrate is 0.4.
8 nm, Ra at the bottom of the pit was 0.50 nm. Further, Ra of the groove portion of the substrate, the land portion of the stamper corresponding to the bottom of the pit, and the peripheral portion of the pit are both 0.61 n.
It was m. On this supporting substrate, Al (100 nm), ZnS.SiO2 (17n
m), GeSbTe (17 nm), ZnS / SiO2
(25 nm), SiO2 (50 nm), ZnS / SiO
2 (50 nm) was provided, and an ultraviolet curable resin layer was further provided thereon to a thickness of 2 μm to form a protective layer.

The light-transmitting layer thus prepared and the supporting substrate were adhered to each other using an adhesive tape (thickness: about 30 μm) for laminating disks made by Nitto Denko Corporation to give a total thickness of 1.2.
mm optical recording medium was prepared. Table 1 shows the disk noise of this substrate.

This medium was placed in a clean room (25 ° C., 5
After being stored in 0% RH) for 3 days, the warpage was measured and the R-Tilt was -0.54 degrees. This medium was put into a temperature / humidity tester at 30 ° C. and 90% RH for 3 days, and the change with time after taking out the medium was measured. The results are shown in FIG. 1, and it can be seen that there is almost no change.

[0051]

Example 2 Pure Ace (100 μm), which is a casting polycarbonate film manufactured by Teijin Limited, was used as the light transmission layer.
m thickness) was used, and an optical recording medium was prepared and evaluated in the same manner as in Example 1 except for the above. R-Ti after storage in a clean room (25 ° C, 50% RH) for 3 days after creation
It was −0.56 degrees. The results after taking out the temperature and humidity tester are shown in FIG. Although the absolute value of the warp is slightly different, it can be seen that in this case as well, there is almost no change with time after taking out. Table 1 shows the results of the disk noise of this substrate.

[0052]

Comparative Example 1 Using the same stamper and resin as in Example 1,
However, the mold temperature was set to 135 ° C. to form the substrate. The groove bottom Ra of this substrate was 0.71 nm, and the pit bottom Ra was 0.75 nm. Table 1 also shows the disk noise measurement results when this substrate was used. If the molding conditions are not suitable even if the same stamper and the same resin are used,
The surface roughness Ra becomes large. Further, it can be seen that when Ra becomes larger than 0.7 nm, the disk noise becomes extremely large.

[0053]

[Comparative Example 2] Polycarbonate resin A manufactured by Teijin Chemicals Ltd.
Using D5503, the same stamper as in Example 1 was molded by an injection compression molding method to obtain a supporting substrate having a thickness of 1.1 mm. Ra of the groove bottom of this substrate is 0.58 nm,
Ra at the bottom of the pit was 0.56 nm. As the light transmitting layer, the same pure ace as in Example 2 was used, and an optical recording medium was prepared by the same method as in Example 1 and evaluated. Table 1 also shows the disk noise measurement results when this substrate was used.
It can be seen that even if Ra is not as large as in Comparative Example 1, if it exceeds 0.5 nm, the disk noise becomes large.

After preparing the medium, in a clean room (25 ° C., 5
The R-Tilt after storing at 0% RH) for 3 days was −
It was 0.50 degrees. The results after taking out the temperature and humidity tester are shown in FIG. In this case, it was found that the warp moved to the + side within a few hours after taking out, and then gradually shifted to the − side to approach −0.5 degrees before the test. The amount of change in warpage during this period was 0.7 degrees, which is larger than those in Examples 1 and 2.

The above-mentioned result is a change in warpage during the dehumidification process. On the contrary, the following measurements were carried out in order to examine how the warpage occurs during the process of absorbing moisture. Since it is not possible to use a warpage measuring device in the temperature and humidity tester for safety reasons, use the method of measuring within 5 minutes after taking it out from the temperature and humidity tester (30 degrees, 90% RH) for convenience. I was there. The optical recording media of Example 1 and Comparative Example 1 were measured for storage time in a temperature and humidity tester for both 8 hours and 100 hours. The results of the R-Tilt are shown in Table 2.

[0056]

[Table 1]

[0057]

[Table 2] In Example 1, even in this case, there is almost no change in warpage. On the other hand, in Comparative Example 1, it was found that the warpage greatly changed in the opposite direction to the case of dehumidification.

In the actual usage of the optical recording medium, it is common for the optical recording medium to move between a place with high humidity and a place with low humidity. At that time, not only does it become stable until 100 hours or more elapses, but also the warp changes rapidly within several hours. In consideration of the moisture absorption process that may occur in reality, the variation in Comparative Example 1 is between -1.15 degrees and 0.2 degrees.
Considering that in an actual environment, there is an environment in which moisture absorption occurs more than at 30 ° C. and 90% RH, the effectiveness of the present invention can be understood more clearly.

As described above, it is understood that the optical recording medium of the present invention is an optical recording medium having less disk noise and less change in warp due to environmental changes.

[Brief description of drawings]

FIG. 1 is a diagram showing a change in warp of an optical recording medium.

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08F 210/02 C08F 210/02 232/00 232/00 C08G 61/08 C08G 61/08 (72) Inventor Nobuaki Kido Yamaguchi 2-1, Hinodecho, Iwakuni-shi, Iwate F-Term in Iwakuni Research Center, Teijin Limited (reference) 4J032 CA34 CB04 CC03 CG02 4J100 AA02P AR09Q AR11Q CA04 DA01 JA36 5D029 KA12 LA03 LB07

Claims (5)

[Claims] 1. An optical recording medium in which at least a reflective film and a light transmitting layer are sequentially formed on a supporting substrate made of a thermoplastic resin, and information is recorded and / or reproduced from the side of the light transmitting layer. The substrate is composed of a polymer having an alicyclic structure in the main chain, and the center line average roughness (Ra) of the bottom surface of the grooves and / or pits formed on the surface of the supporting substrate and / or the light transmitting layer is 0. 10 nm to 0.70
An optical recording medium having a range of nm. 2. The optical recording medium according to claim 1, wherein the thickness of the light transmitting layer is 0.01 mm to 0.2 mm. 3. The optical recording medium according to claim 1, wherein the light transmitting layer is made of a polymer containing an alicyclic structure having no polar group in the main chain. 4. The optical recording medium according to claim 1, wherein the supporting substrate is made of a polymer having an alicyclic structure having no polar group in a side chain. 5. The optical recording medium according to claim 1, wherein the supporting substrate is made of at least one polymer selected from the following (1) to (4). (1) 1 to 99 mol% of the repeating unit represented by the following formula 1A, and 99 to 99 repeating units represented by the following formula 1B.
A copolymer composed of 1 mol%. [Chemical 1] (2) The repeating unit represented by the following formula 2A is 1 to 99 mol%, and the repeating unit represented by the following formula 2B is 99 to 99%.
A copolymer composed of 1 mol%. [Chemical 2] (3) A polymer comprising a repeating unit represented by the following formula. [Chemical 3] [R1, R2 is hydrogen atom, or an aliphatic hydrocarbon group having 1 to 6 carbon atoms, a carboxylate group represented by -COOR ₃ (R ₃ is an aliphatic hydrocarbon group having 1 to 3 carbon atoms) Is. (4) A polymer comprising a repeating unit represented by the following formula. [Chemical 4]